1690 HUMAN ANATOMY. 



It may now readily be understood how, in the presence of the above pre- 

 disposing conditions, hemorrhoids may result from (a) direct pressure upon the 

 veins, as in constipation, pregnancy, ovarian or prostatic enlargements ; (d) indirect 

 pressure through the column of blood, as in hepatic or splenic disease, or from 

 the contraction of the diaphragm and abdominal muscles, as in coughing or lifting 

 heavy weights, or as in straining due to the presence of stricture or \'esical cal- 

 culus or cystitis ; and (c) irritation of the rectum or anus, causing congestion of 

 the hemorrhoidal veins. 



It will be seen that chronic constipation is a possible cause of hemorrhoids 

 under each of the above headings : the fecal masses press upon the veins, irritate 

 the rectal mucosa, and necessitate straining for their expulsion. 



Ulceration of the rectum and anal canal, whether from inflammation or infec- 

 tion following trauma (from indurated faeces or from foreign bodies), or caused by 

 dysentery, tuberculosis, syphilis, or cancer, is of anatomical interest in its relation, 

 first, to the vascular and nervous supply of the parts, and, next, to the surrounding 

 regions. 



The rectum proper is characterized, as Hilton long ago showed, by great 

 distensibility and little sensibility ; the anal canal strongly resists distention and is 

 extremely sensitive. 



The rectum is supplied largely from the sympathetic system through the infe- 

 rior mesenteric and hypogastric plexuses. The anal nerve-supply is chiefly from 

 the sacral plexus, especially the fourth sacral and the pudic nerves, the filaments of 

 which enter the gut at about the level of the ' ' white line' ' which marks the junc- 

 tion of skin and mucous membrane and also the demarcation between the internal 

 and external sphincters. The motor and sensory supply to the anal canal is far in 

 excess of that to the rectum. Corresponding differences are observed in the vascu- 

 lar supply. Although the inferior mesenteric artery brings through the superior 

 hemorrhoidal a relatively large amount of blood to the rectum, it contributes but 

 little to the anal canal, which is richly vascularized by the pudic arteries. 



These facts explain the extraordinary absence of subjective symptoms often 

 observed in cases of large fecal accumulation, malignant growths, or extensive 

 ulceration, when the rectum alone is involved. They likewise explain (through the 

 association of the pudic, the fourth sacral, and other branches of the sacral plexus) 

 the great pain of anal ulceration {fissure') or of inflamed and protruding hemor- 

 rhoids and the associated muscular cramps in the limbs, the vesical irritation or 

 spasm (often causing post-operative retention of urine), the lumbar and iliac pains, 

 and other reflex phenomena so common in anal disease. 



The great power conferred upon the sphincters by their unusually rich nerve- 

 supply, and developed by the resistance they must frequently and necessarily offer to 

 the peristaltic action of the intestines and to the descent by gravity of feculent matter, 

 enables these muscles, especially the external sphincter, through their obstinate and 

 almost continuous reflex spasm, to become not only a cause of the excessive pain of 

 fissure, but also an obstacle to healing. It is therefore usually requisite in the treat- 

 ment of such ulcers to paralyze the sphincters by overstretching, often supplemented 

 by either partial or complete section of the external sphincter. The higher an ulcer 

 in the rectum the more amenable it is to treatment by physiological rest (Hilton). 



Ulceration in the rectum, as elsewhere in the intestinal tract, may result in 

 stricture, or in fistulous connection with neighboring organs or tracts, as the bladder 

 or vagina. 



Lymph infection proceeding from the rectum involves the pelvic and lumbar 

 glands, especially those lying on the front of the sacrum ; if from the anal canal, the 

 upper and inner inguinal glands are involved. The lymphatic distribution, like that 

 of the nerves and blood-vessels, is thus seen to be quite different for the rectum 

 and for the anal canal. 



If infection spreads by vascular rather than lymphatic channels, it usually travels 

 by way of the portal vessels and affects organs connected with the digestive system, 

 especially the liver. Thus a not uncommon sequel of dysentery is hepatic abscess. 

 On the other hand, emboli from external hemorrhoids have been known to enter the 

 general venous circulation and have caused death. 



